File write issue

Fix for:

 * Starting busybox ntpd ... [ ok ]
 * Starting postmarketos-tweakd ...Unable to init server: Could not connect: Connection refused
Unable to init server: Could not connect: Connection refused
Scanning /usr/share/postmarketos-tweaks
  Loading /usr/share/postmarketos-tweaks/power.yml
  Loading /usr/share/postmarketos-tweaks/pinephone.yml
  Loading /usr/share/postmarketos-tweaks/appearance.yml
  Loading /usr/share/postmarketos-tweaks/fonts.yml
  Loading /usr/share/postmarketos-tweaks/phosh.yml
Scanning /etc/postmarketos-tweaks
/sys/class/power_supply/axp20x-battery/voltage_max_design = 4174500
OSError: [Errno 22] Invalid argument

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/pmos-tweakd", line 18, in <module>
    sys.exit(tweakd.main(VERSION, datadir=datadir))
  File "/usr/share/pmos-tweaks/pmos_tweaks/tweakd.py", line 35, in main
    handle.write(value)
OSError: [Errno 22] Invalid argument
 * start-stop-daemon: failed to start `/usr/bin/pmos-tweakd'
 * Failed to start postmarketos-tweakd
 [ !! ]
 * ERROR: postmarketos-tweakd failed to start
 * Restoring rfkill configuration ... [ ok ]